DOE-Based Optimization of Dietary Fiber Extraction Process and Bioactivity Evaluation of Plum (Prunus salicina Lindl.) Processing By-Products

Plum pomace (PP), a key by-product of plum juice processing, is a rich yet underutilized source of dietary fiber. However, its high-value exploitation is severely limited by the lack of efficient extraction and modification technologies. This study optimized the extraction of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) from plum pomace (PP) via Design of Experiments (DOE), and evaluated their modification effects. Alkaline extraction was screened as the optimal method for IDF, and orthogonal experiments determined the optimal conditions: solid-to-liquid ratio 1:20 g/mL, 14 g/L NaOH, 60 °C, and 80 min, achieving a high extraction yield of 62.18%. For SDF, enzymatic extraction was superior, and response surface methodology (RSM) optimized the process to a solid-to-liquid ratio of 1:15.5, 1.0% enzyme dosage, 61.5 °C, and 92 min, with a yield of 29.3%. Physical, chemical, and biological modifications all significantly enhanced SDF’s water/oil-holding capacity, cholesterol/glucose adsorption capacity, and cation exchange capacity. Biologically modified SDF showed the most significant enhancement, with WHC of 5.58 ± 0.05 g/g, OHC of 4.38 g/g, CAC of 7.68 mg/g, and CEC of 3.28 mmol/g. These results provide technical support for the high-value utilization of PP and lay a foundation for its application in functional foods and nutraceuticals.